Question: This mystery bird of the South Pacific was just given a new name! Why? Can you identify this mystery bird's taxonomic family and species? Can you distinguish male from female? Do you live near any of this mystery bird's congeners? If so, which ones?

Response: This is a flock of wandering whistling ducks, Dendrocygna arcuata, a duck ranging throughout the tropical and subtropical Pacific islands; Australia, Indonesia, Papua New Guinea, the Philippines, Borneo and the Pacific Islands. These ducks are gregarious, being found in large groups in deep lagoons, flooded grasslands and in reservoirs behind dams, where they feed on grasses, water lillies and other water plants, on insects and other aquatic animals.

Here's an interesting video of a group of wandering whistling ducks that arrived en masse in a backyard in Australia -- also nice because you can hear the ducks' whistling calls (uploaded on 18 September 2011):

This video captures a group of wandering whistling ducks as they came in to land in the Candaba wetlands (Pampanga, Philippines), providing us with a look at their distinctive hunched flight -- rather like loons, in my opinion:

Wandering whistling ducks and their congeners are odd ducks, looking rather like a hybrid between ducks and geese; having long legs and necks, both sexes have the same plumage, they all have black underwings that are visible in flight, and they have distinctive whistling calls. They typically roost in trees, which gave them their former common name; tree ducks.

These distinctive traits are the reasons that some authorities place them into their own subfamily, Dendrocygninae, within Anatidae (the ducks, geese and swans). Other authorities disagree, either placing them into their own family, Dendrocygnidae, or into a separate tribe, Dendrocygnini, within the goose subfamily, Anserinae.

However these birds are classified, there are eight species, all of which are placed into one genus, Dendrocygna. All species are found in the tropics and subtropics throughout the world.